1. Field of the Invention
The present invention relates to a method of monitoring link performance and diagnosing an active link state in an Ethernet passive optical network (EPON), and more particularly, to a method of monitoring link performance and diagnosing an active link state without interrupting traffic in an Ethernet passive optical network (EPON) while the link is in the active state.
2. Description of the Related Art
An operations, administration, and maintenance (OAM) function is a link diagnosing function enabling an operation to monitor a link state of a network or find a failure location when a link failure occurs. The OAM function includes a loop-back function, a link monitoring function, and a remote failure detecting function. The loop-back function measures link performance between data terminal equipments (DTE). For example, if it is assumed that there is data terminal equipment DTE-A and DTE-B, the data terminal equipment DTE-A (or DTE-B) transmits data and the data terminal equipment DTE-B (or DTE-A) receives and retransmits the data, thereby measuring the link performance.
The link monitoring function is a mechanism for monitoring a transmission/reception state of the link between the DTEs over a period of time.
The remote failure detecting function is a mechanism for reporting a failure state to another DTE when a failure occurs in a remote node.
On the other hand, network transmission standards of an Ethernet passive optical network (EPON) was decided in IEEE 802.3ah standard. The IEEE 802.3ah standard includes a transmission standard of the EPON as well as an OAM function standard of an Ethernet network for point-to-point connection. In the IEEE 802.3ah standard, an OAM sublayer is located above a media access control (MAC) layer and a specific Ethernet frame called an OAM protocol data unit (PDU) is defined, thereby standardizing usable OAM functions.
However, since the loop-back function defined in the IEEE 802.3ah standard blocks or loops back efficient data in the network in a loop-back testing period, the efficient data may be lost. Although test data is generated and the loop-back function is performed using the test data, data cannot be transmitted during the loop-back process and thus the link monitoring function can not be performed during an active period of the link. Also, in the IEEE 802.3ah standard, the link monitoring function is not separately defined, and, if necessary, a query on performance information of a remote node can be performed using the OAM PDU during the loop-back process. That is, in the prior art, since the loop-back function in the IEEE 802.3ah standard causes the loss of efficient data, it is not suitable for monitoring the performance of a link which is in an active state.